Colorant testing solvents

Blood, brain, lungs Solvents (methanol, toluene, hydrocarbons) Color tests GC Head-space LEE GC GC-MS... 

The wrapping is removed at the end of the 24-h exposure period. The test substance skin site is wiped to remove any test substance still remaining. When colored test substances (such as dyes) are used, it may be necessary to wash the test substance from the test site with an appropriate solvent or vehicle (one that is suitable for the substance being tested). This is done to facilitate accurate evaluation for skin irritation. 

Colors of adsorbed Hammett indicators can be used to bracket the H0 of a solid surface in the same way that the colors of more conventional acid-base indicators are used to bracket the pH of an aqueous solution. Thus, when an acid color is observed for the adsorbed indicator, the H of the solid surface is equal to or lower than the pKa of the indicator. As an example, a solid surface that has an H0 that lies between + 1.5 and -3.0 gives an acid color with benzeneazodiphenylamine (with a pKa of + 1.5) and a basic color with dicinnamalacetone (pKa of - 3.0). Color tests are made by adding 3-5 ml of dry solvent (e.g., benzene) to roughly 0.1 g of dried, powdered solid in a test tube, adding a few drops of a 0.1% solution of indicator in benzene, mixing the resulting suspension, and noting the color formed on the powdered solid. 

Critical limitations are those determining the separation and identification of spots. If a spot remains unresolved in three different solvent systems, it may be considered homogeneous. If its position coincides in these solvent systems with that of a known, run simultaneously, its identity is then considered established. These criteria should, however, be buttressed by as many other criteria of identity as are available, such as highly specific color tests, chemical alteration, or better still, where possible, isolation of the material in quantity sufficient to permit employment of classical identification methods. That there is need for these further criteria was shown by Levine and Chargaff,212 who noted that l-amino-2-hydroxypropane and 2-amino-l-hydroxypropane have the same Rf values in five different solvent systems. 

The blue benzophenone radical anion (the first recognized radical anion [65]) is well-known as a color test for the absence of water and oxygen from ether solvents over Na. In the presence of water, it forms the colorless pinacol by dimerization of the ketyl radical Ph2C(0)H (i.e. the protonated form of the radical anion) [66]. In the presence of dioxygen it is rapidly oxidized back to benzophenone, and thus removes traces of O2 from N2 [67]. It has been very little used as a stoichiometric... 

Dry carbon dioxide gas is bubbled slowly under the surface of a cooled tetrahydrofnran solution of one mole of benzylmagnesium chloride complex until a negative Gilman Schultze color test results. The mixture is then heated to reflux, the addition of carbon dioxide is discontinued, and a further one mole of benzylmagnesium chloride complex is added rapidly (over a period of 20-40 minutes). After completion of addition, the mix is refluxed for 2-4 hours, cooled, and 100-200 mL. of toluene added. The organic solution and suspension is extracted by one 100-mL. portion of water and one 100-mL. portion of 10% sodium carbonate. On acidification of the aqueous extracts, phenylacetic acid is obtained. The organic layer is subjected to distillation to remove solvents and then to vacuum distillation. Dibenzyl ketone and a small amount of tribenzyl carbinol are obtained. 

Test lube 1 contains w-hexane (or w-heptane), test tube 2 CS2 in both cases a deep violet color is formed. Test tubes 3 and 4 arc filled with toluene and cyclohexene respectively iodine colors these solvents wdne-red. Test tube 5 contains acetone and test tube 6 diethyl ether here the iodine solutions are yellow. 

The formation of the reagent can be checked by qualitative color tests or by titration. Eor this purpose the volume of the solution should be measured or estimated as accurately as possible. An aliquot is taken, cautiously hydrolyzed and titrated with HCl against methyl-red indicator. If desired, this may be followed by a titration of total Mg with complexon (ethylenediaminatetraacetic acid) the difference between total and basic Mg is a measure for the xs MgBt2 formed in, e.g., radical side reactions. The radicals lead to radical coupling products, R—R, but they may also disproportionate, attack the solvent or rearrange ... 

In our early studies we observed with R. Jones and others, some significant solvent effects on coordination or complex formation as they influenced the reactivities of some organometallic compounds. They had been known for some time, and appeared rather striking when examined in connection with Michler s ketone and the color test. From our study it appeared that the order of decrease in relative reactivity and increase in tendency to form coordinate compounds with ketones was PhLi, PhMgBr, PhjGa. 

After the separation of the sugars on the filter paper by the different solvents, the sugars are identified by their relative position and by specific color tests. The position of the sugar spot is generally given in terms of a constant, Rf, which is defined as the ratio of the distance moved by the spot to the distance moved by the solvent front. Often it is impossible to determine the distance moved by the solvent front (it may be permitted to... 

Unlike the situation noted for marijuana, the morphology of mushrooms and peyote is normally not used as part of their identification, due to the more complex botanical challenge. The plant-matter matrix of peyote and psilocin mushrooms makes the use of color tests impractical, unless the tests are apphed to the extract. In most cases, ethanol or methanol is the extraction solvent of choice for dried plant matter. Some laboratories heat the methanol prior to extraction. The peyote button, and sometimes mushrooms, must be grotmd with coffee grinders or similar equipment or must be macerated prior to extraction. Cleaning these appliances between uses is crucial to prevent cross-contamination. The extracts are then amenable to TLC and instrumental confirmation by GCMS. 

Eastness to solvents The test is carried out on the pigment powder. A closed filter bag containing 0.5 g of the pigment is immersed in 20 ml of the test solvent for 24 hours. The color change of the solvent is compared against a standard color sclae according to DIN EN 20105-A03 (formerly DIN 54002)... 

Tolerance to an individual solvent is tested by enclosing a certain amount of pigment powder in a piece of filter paper, which is then immersed in the organic solvent for a given amount of time. The extent of coloration of the test solvent indicates the solvent fastness of the pigment. 

Procedure The tested solvent (0.5 ml) is added slowly to 5 ml of ice-cold nitration mixture in a 150-ml Erlenmeyer flask, which is then stoppered and allowed to stand for 1 hr. The reaction mixture is then diluted, tmder steady cooling, with 50 ml of water, and 15 ml of 30% sodium hydroxide solution is added until the reaction of the mixture is alkaline to litmus. The mixture is then transferred to a separatory funnel and thoroughly extracted with 30 —40 ml of water." The ethereal layer is then put into a porcelain dish and the ether is evaporated carefully. The residue is dissolved in 50 ml of butanol. A part of this solution is put into a test tube and mixed with sodium hydroxide solution. The appearance of a red to violet color means a positive reaction. 

All these facts can be utilized in the application of the color test. Generally, the reaction is carried out in different solvents, sometimes with the addition of pyridine. Phenols can be differentiated according to the strength with which they form chelate bonds in the presence of acetic acid or with a suspension of ferric hydroxide in water or methanol with subsequent acidification. A list of chelate-forming substances is given in Table 5. 

So now we have this solvent containing ketone, dried with MgS04... Not being able to vac-distill today, took about 50 mis of solvent/ketone and placed in beaker on stir plate and boiled off the solvent. The resulting oil was a nice reddish-orange color. Had a very unique smell too. Took about 2 grams worth of this ail, added to a test tube containing a saturated solution of sodium bisulfite... In less than 60 seconds the oil precipitated into a whitish yellow mass (very similar to what acetone would do if added to a bisulfite solution). Never had this quick of a crystallization. Not... 

Thermal Properties. The thermal stabiUty of cellulose esters is deterrnined by heating a known amount of ester in a test tube at a specific temperature a specified length of time, after which the sample is dissolved in a given amount of solvent and its intrinsic viscosity and solution color are deterrnined. Solution color is deterrnined spectroscopically and is compared to platinum—cobalt standards. Differential thermal analysis (dta) has also been reported as a method for determining the relative heat stabiUty of cellulose esters (127). 

Testing is undertaken by several methods, including chloroform extraction and use of a sulfonphthalein dye (absorbance of yellow-colored complex using bromophenol blue and bromocresol green) or the use of eosin (sodium tetrabromofluorescein) solution in acetone and tetrachloroethane solvent. After shaking with a citric acid buffer and eosin addition, upon standing the lower layer turns pink if filmer is present. Subsequent titration with Manoxol OT (sodium dioctyl sulfosuccinate) quantifies the filmer, with loss of the pink color indicating the end point. 

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